This invention relates to an oil supply device for use, for example, in a rotary machine, such as a vacuum pump, particularly a rotary piston pump (Roots pump) wherein the pump drive shaft has a terminal stub which extends into a chamber partially filled with oil.
An oil supply device of the above-outlined type is disclosed in published PCT application No. WO83/04075. The oil supply device is constituted by a self-drawing lateral channel pump. It is a disadvantage of this arrangement that a pump of this type has a relatively high input energy requirement and further, displacement pumps are not particularly suitable for operation in vacuum, because they require a relatively high intake level in vacuum and they entrain gas bubbles because of the frequent presence of foam in the oil chamber due to pressure fluctuations. The result is cavitation which not only leads to a noisy operation but may cause damages as well.